Metal 8-hydroxyquinolate complexes as stabilizers for poly(phosphazenes) to inhibit thermal degradation at elevated temperatures

ABSTRACT

Stabilization of polyphosphazenes against thermal degradation is acheived by the incorporation of organometallic compounds, particularly metal complexes of 8-hydroxyquinolates or other metal complexes in such phosphazene polymers.

United States Patent .191 Kyker [111 3,867,341 [4 1 Feb. 18, 1975 METAL S-HYDROXYQUINOLATE DOMPLEXES AS STABILIZERS FOR POLY(PHOSPHAZENES) T0 INHIBIT THERMAL DEGRADATION AT ELEVATED TEMPERATURES Gary Stephen Kyker, Uniontown, Ohio The Firestone Tire & Rubber Company, Akron, Ohio Filed: Sept. 28, 1973 Appl. No.1 401,769

Inventor:

Assignee:

US. Cl ..260/45.75 R, 260/458 NW, 260/4575 W, 45.75 G Int. Cl C08g 51/62,

Field 01 Search 260/2 P, 45.75 R, 45.8 NW

Primary ExaminerV. P. Hoke [57] ABSTRACT Stabilization of polyphosphazenes against thermnl degradation is acheived by the incorporation of organometallic compounds, particularly metal complexes of 8-hydroxyquinolates or other metal complexes in such phosphazene polymers.

9 Claims, No Drawings METAL [FHYDROXYQUINOLATE COMPLEXES AS STABILIZERS FOR POLYtPHOSPHAZENES) TO INHIBIT THERMAL DEGRADATION AT ELEVATED TEMPERATURES Allcock et :11 3,370,020 issued February 20, 1968 Rose 3,515,688 issued June 2, 1970 Reynard et a1 3,700,629 issued October 24, 1972 Rose et a1 3,702,833 issued November 14, 1972 In the present Specification, the term poly(phospha zenes) is intended to include the polymers described in the above noted patents and any other such materials represented by the general formula /X 2% {w n in which X and X each represent monovalent groups including alkoxy, substituted alkoxy, especially fluoroalkoxy, aryloxy, substituted aryloxy, amino, and other such groups, and X and X may be the same or they may differ, and n is an integer greater than 3 and up to 50,000.

Previous efforts to inhibit the thermal degradation of such poly(phosphazenes) have been directed to the incorporation therein of basic metal oxides or similar compounds or of metal dithiocarbamates. Metal oxides are insoluble in these polymers and hence have a relatively low level of activity. Metal dithiocarbamates are partially soluble in these polymers, but are limited in use by the fact that they promote crosslinking (gelation) on extended aging and they are incompatible with peroxide curatives.

The principal object of the present invention is the protection of poly(phosphazenes) from thermal degradation by the addition of stabilizers which are compatible with the poly(phosphazenes) and which are effective when used in smaller quantities than the amounts of insoluble stabilizers heretofore used.

Another object of the invention is to stabilize poly(- 5 phosphazenes) against thermal degradation by means of an additive which does not promote gel formation on external aging and which does not adversely affect vulcanization of the polymers.

A further object of the invention is to provide a stabi lizer which can be added to the polymer, in solution, or

which can be added to the polymer in any of the usual mixing apparatus such as mill, Brabender, or Banbury mixing or kneading, without special procedures.

These and other objects of the invention will become apparent from the description of preferred embodiments of the invention which are intended to illustrate the same and are not intended to limit the invention in any way.

EXAMPLE 1 Bis(8-hydroxyquinoline) zinc 11 was synthesized by dissolving zinc chloride (ZnCl in distilled water and adding two equivalents of S-hydrdxyquinoline dissolved in ethanol to the aqueous solution of zinc chloride. A yellow solid precipitated from the solution and was recovered from the solution, washed free of zinc chloride, using distilled water and then dried in a vacuum oven at 60C.

Portions of the recovered bis(8-hydroxyquinoline) zinc ll hereinafter designated (8-HQ) Zn were blended with a fluoroalkoxy polyphosphazene represented by the formula; and hereinafter designated designated 0CH2CF3 C2FC5F(T): 15 N P n(3-50,ooo) 0on CF2) 3-CF2H under both heterogeneous and homogeneous conditions, (i.e. in acetone and in tetrahydrofuran) in amounts ranging from 1 to 4 mole based on the polymer.

The solvent was then removed and the dry elastomer aged in a forced-air oven at 300Fsamples were periodically removed for measurement of viscosity (DSV) and gel content (see Table l for results). From inspection of this data it is quite evident that this stabilizer extends the service life of this elastomer to a large extent at 300F in air 1,000 hrs.). This stabilizer functions equally well in all types of poly(phosphazenes) evaluated.

Table 1 Dilute Solution Viscosity After Aging At 300F Sample No. A B C D E F G Mole 0 1.0 .0 4.0 1.0 .0 4.0 Hrs. Aged In samples B, C, and D, stabilizer and polyphosphazene were mixed in acetone (heteogeneous mixing) and in samples E, F, and G, stabilizer and polyphosphazene were mixed in tetrahydrofuran (homogeneous mixing).

% Gel in all samples was EXAMPLE 2 Stabilization of C C (T) Copolymer With Metal EXAMPLE 4 A vulcanized Cf C (T) U terpolymer gum was stabilized with (8-l-lQ) Zn. Table IV sets forth a comparison of the properties of two otherwise identical vulcanized gums one of which includes the stabilizer and the other does not.

8-Hydroxyquinolates Table IV Selected metal 8-hydroxyquinolates were blended g t lfi (P y wt.) A B with C C (T) copolymer in acetone. The solvent was 2 2 then removed and the sample dried in vacuo. These Dicumyl Peroxide 1 1 samples were then aged at 300F in a forced air oven l 5 (8'HQ)2Z 0 qt 1 q and samples periodically removed for viscosity and gel Stress-Strain (Unaged) Value Change VfllUlZ Cha nge measurements (see Table II). From inspection of these 2+ (Cure 30 mm. at 320F) data 1t apparent that 8-hydroxyqumolates of Mg (Post Cure 24 hrs, at Al, and Cr are effective in retarding the thermallyfg l d l 62 c o uus ps1 60 induced decomposltton of th1s polymer. Smile Strength (psi) 230 260 ongation I60 I80 EXAMPLE 3 Aged 240 hrs. at 300F F 100% Modulus (psi) 30 -5l.7 47 2l.7 Stab1l1zat1on of C C (T) U (U Cure Site) Tensilestrength (psi) 140 200 30 0 Terpolymer with Metal 8-Hydroxyqu1nolates Elorhgaztll%nh(%) 190 1s.s 165 3.3

Age rs. at 350F Metal 8-hydroxyqu1nolate stablhzers were thor- 5 100% Modums (psi) I8 66 +10, oughly mixed with samples of polymer in acetone. The Tensile Strength (P 5 .4 226 13.1 Elongation (72) 205 +28.l I65 8.? samples were stripped of solvent then dr1ed in a vac- Aged 336 hm at s uum oven. These samples were then aged at 300F in 100% Modulus (psi) 16 -74 1 47 a forced air oven and samples were periodically withg i g ia 214 17.7

r r O a 10 drawn for v1scos1ty [DSV] and gel measurements (see 30 A sardcness Table III). From inspection of this data, it is evident Unagcd 21 that 8-hydroxyquinolates of K, Zn, Mg and Al g zg 318 23 55 g g% 2 s are effective stabilizers agamst heat-1nduced degrada- L7 Comeression Sm tion of this polymer. 70 hrs. at 300F 23 13 Table ll Dilute Solution Viscosity After Aging at 3()()F Sample Stabilizer Amount hr p Hours 0 24 4x 72 120 240 4021 4x0 720 1000 1 Metal 8-HQ None 2.14 0.80 0.54 0.48 0.42 0.52 0.25 0.25 0.15 0.15 2 Mg+2 0.5 2.07 1.41 1.09 0.95 0.70 0.60 0.47 0.46 0.35 3 Mg+2 1.0 2.21 L85 1.34 1.40 1.29 0.95 0.84 0.76 0.50 4 M +z 2.0 2.07 1.90 1.66 1.94 1.34 0.94 1.57 1.72 1.68 1.07 5 Al+3 0.5 2.11 1.37 0.91 0.83 0.58 0.49 0.39 0.30 0.30 6 Al+3 1.0 1.94 1.21; 0.77 0.97 0.31 0.83 0.71 0.76 0.67 0.25 7 Al+3 2.0 2.16 1.32 1.16 1.17 0.88 0.71 0.62 0.63 0.55 0.45 8 0+3 0.5 2.23 0.53 0.76 0.75 0.98 9 04-3 1.0 2.04 0.60 0.50 0.52 0.66 10 cr+3 2.0 2.32 0.79 0.54 0.51 0.53 11 cr+3 4.0 2.28 0.70 0.413 0.521 0.79

7s Gel is 0.0 in all samples Table lll EXAMPLE 5 I a Stabilization of C C "(T) Copolymer Stock Against Dllute Solut1on V1scos1ty After Agmg at 300 F Heat Degradation at 0 in Air Aging Time (H's) A typical silica-reinforced and peroxide-cured stock M 0 72 120 312 316 Stabilizer Ole was compounded for a control (A) (see Table V). M6011 8-HQ 0 2.08 1.03 0.87 0.66 0.62 Stock (B) was the same as (A) except for the addition 5'8; lg; lg; Hg of one phR of (8-HQ) Zn during the mixing process 1 +1 2.0 1.77 1.42 1.29 089 0.75 (Brabender Mixer). From inspection of the stress/- 3'82 1'28 strain and Shore A Hardness data it is apparent that the zn+2 2:0 1:96 1:73 1:69 :47 1:53 addition of (8-HQ Zn improves both the normal as $23 52 lg; well as the heat-aging propertles of th1s stock.

g Mg+2 2.0 2.08 1.86 1.89 1.72 1.64 Al+3 0.5 2.05 1.70 1.66 1.34 1.30 EXAMPLE 6 Al+3 1.0 1.90 1.63 1.62 1.32 1.21 F p Al+3 20 104 L26 L12 L49 '2 Stab1l1zat1on of C C (T) U Terpolymer Stock Agamst 1: Gel is 0.0 in all samples.

Heat-Degradation at 300-350F in Air By Use ofZn, Mg and Al 8-Hydroxyquinolates A typical silica-reinforced and peroxide-cured stock was compounded for the control (A). Stocks B, C and D were of the same basic composition except for the addition of Zn, Mg and Al S-hydroxyquinolates l phr) during the mixing process (Brabender). From inspection of the stress/strain data it is apparent that these stabilizers do not interfere with the peroxide cure. Furthermore, these stabilizers afford a substantial improvement in the retention of physical properties upon aging at 300-350F in air.

A typical carbon-black reinforced and peroxidecured stock was used for the control (E) in the next series of experiments. Stocks F and G were basically the same as E except for the addition of Zn and Mg 8- hydroxyquinolates. From inspection of the stress/strain data it is obvious that the addition of these stabilizers results in large improvements in both normal and aged properties. The data is shown in Table VI.

Table V EXAMPLE 7 Stabilization of CJC (T) U Terpolymer Stock (Silane-Treated Clay Reinforced and Peroxide Cure) With (8-I-IQ)2Zn Stock (A) was compounded as the control whereas Stock (B) was of the same basic composition except for the addition of(8-HQ)zZn (l phR). From inspection of the stress-strain and Shore A Hardness data it is apparent that this stabilizer improves stress/strain, compression set, hardness and heat-aging properties at 300F in air. The data is shown in Table VII.

EXAMPLE 8 Stabilization of A C C (T) U Terpolymer Stock Against Heat-Degradation at 400F in Air By Use of Zn and Mg 8-I-Iydroxyquinolates There was no control for these studies but previous experiments had revealed that stocks without stabilizers were hrghly degraded after 120 hr. at 400F. In con- Compound A B trast, these stocks [A(l phR of (8-I'IQ) Zn) and EU P l C r T 100 0 100 0 phR of (8-I-IQ) Mg)] still have fairly high 100% moduli 5 15353 5 I 3030 m (6 37 and 5 2 psi) and tensile strength (1050 and 1037 g 6.0 6.0 ps1) after aging 120 hr. at 400 F Therefore, it 1s appar- Cicum l Peroxide 6 0 6 0 g Zn ent that these stabilizers greatly improve heat-aging Aged Stress/Strain properties for these stocks at 400F in air. The data is Cure min. at 320F Post Cute 24 hrs. at 212F Show m Table VIII Modulus Table v Unaged 5O 30 120 hrs. at 300F 110 1 240 hrs. at 300F 100 I20 Compound A B 100% Modulus Unaged Polymer 100.0 100.0 hrs. at 300F 165 Burgess KB 400 40.0 240 hrs. at 3001= 200 15 6 0 6.0 Tensile Strength (psi) 35 g gy e 3.0 5.8

. r n P o I590 Aged St ress/Strain 1-0 hrs. at 300 F 955 1500 cm 30 min at 320,? 240 hrs. 111 300F 800 1260 Post Cure hrs m 212,]: v f r 'yll 44 S20 50% Modulus (psi) nuge 120 hrs. at 300? 410 510 40 gg fg m 7 3 300 F 420 475 240 hrs. at 3001= degraded 75 shore A Hardness 100% Modulus Si) Cure 30 min. at 320F 0 Post Cure 24 hrs. at 2l2F at 0 i imaged 240 hrs. at 300 1 degraded 700 300,}: 52 56 Tensile Strength (psi) 240 hrs. at 300 F 52 (H 45 Unaged 625 750 Table VI Compound A B C D E F G Polymer CJC,"(T)U 100 100 100 100 100 100 100 Silanox IO! 20 2O 20 2O Acrosil 300 5 5 5 5 HAF Black 25 25 25 MgO 6 6 6 6 6 6 6 Dicumyl Peroxide 2 2 2 2 2 2 2 (SLHQhZn 1 1 (B HQhMg 1 1 (R-HQhAI 1 Stress/Strain 100% Modulus (psi) Unaged 1 140 670 855 885 400 405 590 240 hrs. at 3001= 895 1300 1120 675 140 265 315 120 hrs. at 350F 595 680 715 560 62 165 170 Tensile Strength (psi) Unaged 1780 1660 1560 1610 1590 1530 1740 240 hrs. at 3001= 1525 1460 1560 1530 300 945 1160 120 hrs. at 350F 885 1110 1165 1025 75 225 270 Elongation 7r Unaged 110 130 125 205 205 :90 240 hrs. at 300F 180 170 150 245 265 240 120 hrs. at 350F 130 155 150 270 245 245 Shore A Hardness Unaged 74 72 73 69 47 44 120 hrs. at 300F 7s 75 77 72 51 47 240 hrs. at 300F 79 77 75 71 5.7 53 72 hrs. at 350} 77 70 75 72 50 40 l20hrs.21l 350F 711 77 711 75 50 50 Table VII-Continued Compound A B 120 hrs. at 300F 12 840 240 hrs. at 300F degraded 800 mm Unaged 250 105 120 hrs. at 300F 200 I05 240 hrs. at 300F degraded 120 ASTM Compression Set (method B 22 hrs. at 212F) 75 I3 Shore A Hardness Unaged 34 51 120 hrs. at 300F 36 51 240 hrs. at 300F 34 54 Table VIII Compound A B Polymer CJCJYTJU I I00 Silanox IOI 30 30 MgO 6 6 Dicumyl Peroxide 2 2 (8-HQ) Zn 2 (8-HQ)zM 2 Stress/Strain Cure 30 min. at 320F Post Cure 24 hrs. at 212F W Unaged 862 725 120 hrs. at 400F 637 562 240 hrs. at 400F 500 465 240 hrs. at 350F 900 950 336 hrs. at 350F 896 809 336 hrs. at 300F 760 912 672 hrs. at 300F 902 960 Tensile Strength (psi) Unagcd 1500 887 120 hrs. at 400F I050 I037 240 hrs. at 400F 730 705 240 hrs. at 350F I688 I250 336 hrs. at 350F I244 I183 336 hrs. at 300F I938 I925 672 hrs. at 300F I738 I797 Elongation Unagcd I20 90 120 hrs. at 400F I60 I70 240 hrs. at 400F I75 I75 240 hrs. at 350F 150 I15 336 hrs. at 350F 130 I40 336 hrs. at 300F I60 I45 672 hrs. at 300F I50 I40 Shore A Hardness Unaged 66 65 240 hrs. at 400F 73 76 336 hrs. at 400F 80 75 240 hrs. at 350F 72 70 336 hrs. at 350F 74 71 336 hrs. at 300F 71 71 672 hrs. at 300F 72 72 EXAMPLE 9 Stabilization of [(C H O) (C H O) U P=N],, Terpolymer Stock with (8-HQ)2 Zn This terpolymer was treated with (8-HQ)2Zn (3 mole in THF (homogeneous), stripped of solvent then dried in a vacuum oven. A small portion of this stabilized gum was aged at 300F in a forced air oven and samples were periodically withdrawn for viscosity [DSV] and gel measurements (see Table IX, footnotes 2, 3). From inspection of this data, it is apparent that (8-HQ) Zn is an active stabilizer for this polymer just as it was for CJC 'tT) and CJ'CJIT) (U)-type polymers. Both the control and the stabilized gums were then compounded with reinforcing silicas and curing agents in a Brabender Mixer. Both the sulfuraccelerator cured stock (B) and the peroxide cured stock (D) showed a large improvement in normal and aged (300F) stress/strain properties relative to the Q l P I Q I in which Q and Q represent monovalent alkoxy (C I-I O) and aryloxy (C I-l O) groups randomly distributed along the P=N- backbone, and wherein a group with some unsaturation to serve as a cure site,

also randomly distributed along the chain, is present in place of some of the Q or Q groups.

Table IX Formulation A B C D Polymer H10 100 I00 I00 Silanox I01 40 40 40 40 Aerosil 380 5 5 5 5 Zinc Oxide 5 5 5 5 Sulfur 0.5 0.5 Accelerators 5.0 5.0 Dicup 40C 2.0 2.0 Stabilizer (8-HQ) Zn 3.0) 3.0) mole 7() mole Q I A ed Stress/Strain Cure (l0 min. at 320F) Post Cure (hr. at 212F) None None 24 14 50% Modulus( si) Unaged 300 I90 240 370 120 hrs. at 300F I75 300 I00 362 240 hrs. at 300F 125 250 75 250 100% Modulus( si) Unaged 545 I20 hrs. at 300F 287 500 I50 240 hrs. at 300F I50 500 600 Tensile Stren th Unaged 615 920 401) 575 120 hrs. at 300F 400 650 167 425 240 hrs. at 300F 200 500 75 600 Unaged 75 I30 65 57 120 hrs. at 300F I92 I55 90 60 240 hrs. at 300F I30 100 50 I00 Control polymer no stabilizer Polymer treated with 3 mole I IR-HOJJn in THF (homogeneous). Hcal Aging of Polymer (0.071 Gel in all Samples) (DSV) 0 hr. 3.54 3.27 24 hr. 0.35 0.80 48 hr. 0.3I 0.83 240 hr. 0.15 0.34

In the preceding examples various tradenames and abbreviations are utilized, the meanings of which are as follows:

phr parts by weight per 100 parts of rubber (polyphosphazcne) by weight Silanox Hydrophobic fumed silica Burgess KE Surface trcatcd anhydrous aluminum silicate Aerosil Fumcd silica Further, it should be understood that in addition to being applicable to the thermal stabilization of phos phazene copolymers, i.e., polyphosphazenes in which IL. )n

wherein n represents an integer from 3 up to about 50,000 and X and X each represent a monovalent substituent selected from the group consisting of alkoxy, substituted alkoxy, aryloxy, substituted aryloxy, hydroxy and amino, and X and X are randomly distributed along the P=N backbone and the polyphosphazene includes one or two or more randomly distributed groups and an organometallic compound compatible with said polyphosphazene and present in an amount sufficient to stabilize said polyphosphazene against thermal degradation, said organometallic compound being a metal 8-hydroxyquinolate.

2. Polyphosphazenes according to claim 1, wherein the metal is selected from the group consisting of alkali metals, alkaline earth metals including Mg, and Al, Zn and Cr.

3. Polyphosphazenes according to claim 1, wherein the stabilizer is present in an amount between 0.05 and 5.0% by weight.

4. The stabilized polyphosphazenes of claim 1, wherein X and X are fluoroalkoxy or fluoroaryloxy groups.

5. Elastomers consisting essentially of the stabilized polyphosphazenes of claim 1.

6. Plastics consisting essentially of the stabilized polyphosphazenes of claim 1.

7. Thermoplastic elastomers consisting essentially of the stabilized polyphosphazenes of claim 1.

8. Fibers consisting essentially of the stabilized polyphosphazenes of claim 1.

9. Vulcanized articles consisting essentially of the stabilized polyphosphazenes of claim 1.

2 3 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Pa tent No 5 867 EW] Dated February 1 8 'l 975 Inventor) Gary Stephen Kyker It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Column 2, Line 555, delete "designated".

In Column 4, Table IV, Line 24, under the heading Change" first occurrence, "-18.8" should read +l8.8

In Column 5, Table V, Line 25, under the heading "Compound",

"Cicumyl" should read Dicumyl Signed and sealed this 29th day of April 1975.

(SEAL) Attest:

C. MARSHALL DANN Commissioner of Patents and Trademarks RUTH C. MASON Attesting Officer 

1. A POLYPHOSPHAZENE COMPOSITION STABLIZED AGAINST THERMAL AGING COMPRISING A POLYPHOSPHAZENE REPRESENTED BY THE GENERAL FORMULA: -(P(-X)(-X'')=N)NWHEREIN N REPRESENTS AN INTEGER FROM 3 UP TO ABOUT 50,000 AND X AND X'' EACH REPRESENT A MONOVALENT SUBSTITUENT SELECTED FROM THE GROUP CONSISTING OF ALKOXY, SUBSTITUTED ALKOXY, ARYLOXU, SUBSTITUTED ARYLOXY, HYDROXY AND AMINO, AND X AND X'' ARE RADOMLY DISTRIBUTED ALONG THE -P-N- BACKBONE AND THE POLYPHOSPHAZENE INCLUDES ONE OR TWO OR MORE RADOMLY DISTRIBUTED GROUPS AND AN ORGANOMETALLIC COMPOUND COMPATIBLE WITH SAID POLYPHOSPHAZENE AND PRESENT IN AN AMOUNT SUFFICIENT TO STABILIZED SAID POLYPHOSPHAZENE AGAINST THERMAL DEGRADATION, SAID ORGANOMETALLIC COMPOUND BEING A METAL 8HYDROXYQUINOLATE.
 2. Polyphosphazenes according to claim 1, wherein the metal is selected from the group consisting of alkali metals, alkaline earth metals including Mg, and Al, Zn and Cr.
 3. Polyphosphazenes according to claim 1, wherein the stabilizer is present in an amount between 0.05 and 5.0% by weight.
 4. The stabilized polyphosphazenes of claim 1, wherein X and X'' are fluoroalkoxy or fluoroaryloxy groups.
 5. Elastomers consisting essentially of the stabilized polyphosphazenes of claim
 1. 6. Plastics consisting essentially of the stabilized polyphosphazenes of claim
 1. 7. Thermoplastic elastomers consisting essentially of the stabilized polyphosphazenes of claim
 1. 8. Fibers consisting essentially of the stabilized polyphosphazenes of claim
 1. 9. Vulcanized articles consisting essentially of the stabilized polyphosphazenes of claim
 1. 